Immunopathology II Flashcards
What is an allergy?
Hypersensitivity disorder of the immune system -> reaction to normally harmless environmental substances
What is the subdivision of hypersensitivity? (2)
- Allergic hypersensitivity = immunologically mediated
- Non-allergic hypersensitivity = non-immunologically mediated
What are the types of immunological hypersensitivity reactions?
- Type I = IgE-mediated degranulation of mast cells
- IgG-mediated response to antigens presented on the cell surface
- IgG-mediated response to deposition of immune complexes
- Type IV = T-cell mediated response
Which further subdivision can be identified within type I allergies? (2)
- Atopic = genetic predisposition
- Non-atopic
Which type I allergies are often not atopic? (3)
- Insect venom
- Helminths
- Drugs
Which type I allergies are often atopic?
- Asthma
- Rhinoconjunctivitis
- Urticaria
In which cases is IgE elevated in the serum? (3)
- Physiological response to parasitic infections
- Hyper-IgE-syndrome
- IgE-mediated diseases
Are mast cells found in circulation?
No, only in tissue
Which processes are triggered by mast cell degranulation? (3)
- Contraction of smooth muscle
- Vasodilation and increased vascular permeability
- Irritation of mucous membranes
Which kind of T-cell response is an IgE-mediated allergic reaction?
Th2
What is the role of Th2 cells in IgE-mediated allergy? (3)
- Induces class switching of B-cells to IgE
- Attracts eosinophils to the site of allergen exposure
- Produces cytokines upon allergen exposure
What is the difference between sensitization to an allergen and allergy?
Sensitization = IgE-production
Allergy = IgE-mediated clinical manifestation upon contact with allergen
What is needed for an allergy to develop?
Repeated exposure to allergen
What is the hygiene hypothesis?
Insufficient exposure to infectious pressures during childhood leads to a disrupted balance between Th1/Th2-responses
What is an important characteristic of type I allergens? Why do type I allergens have this property? (3)
Capable of penetrating epithelial barriers
1. Low molecular weight
2. Good solubility in aqueous milieu
3. Enzymatic activity
What is an important immunological factor for retaining tolerance to allergens?
Tregs
What are the possible diagnostics of IgE-mediated allergies? (4)
- Monoplex -> analysis of specific IgE through ELISA
- Functional -> basophil activation test
- Micro-array -> using a chip containing many allergens
- CLinical evaluations
Which clinical evaluations of IgE-mediated allergies are available? (2)
- Skin prick test
- Oral food challenge = gold standard
What are the treatment options of type I allergy?
- Elimination of allergen exposition
- Medication
- Specific immunotherapy
Which medications are (amongst others) available to treat type I allergic reactions? (2)
- Anti-histamines
- EpiPen
How does the specific immunotherapy for IgE-mediated allergies work?
Subcutaneous injection of escalating dosages of allergen, leading to Treg induction
What makes that coeliac disease is on the middle ground between an allergy and an auto-immune disease?
Allergic characteristic: triggered by relatively harmless exogenous antigen
Auto-immune characteristic: production of auto-antibodies
What is the treatment of coeliac disease?
Stopping gluten intake
What is the histopathological effect of coeliac disease?
Villus atrophy and flattening of the intestinal mucosa
Which HLA-genes are associated with coeliac disease? (2)
- HLA-DQ2.5
- HLA-DQ-8